Temperature and low water monitoring for boiler systems

ABSTRACT

A dual functionality temperature control measurement and low water cutoff measurement system is taught within a single tapping to a boiler. This dual functionality combines a low water cutoff and temperature sensor into one control utilizing a sensing element suitable for use in a single existing tapping for a boiler. Independent of low water functionality, the temperature sensor is also capable of monitoring temperature as a replacement probe in an existing temperature sensor-only well. A conductive member provides a compression fit inside the probe well for thermistors, while simultaneously providing conduction with the well interior for a low water cutoff signal in a two-conductor well.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to safety devices that automaticallycut-off the burner operation of a hot water boiler. More specifically,the present invention relates to the type of boiler used in residentialand light commercial heating applications that include a control systemfor monitoring both the temperature and level of the water in theboiler. The system allows these attributes to be measured through asingle probe inserted into the boiler through a single tapping.

2. Description of Related Art

In conventional boilers of the type used in residential and lightcommercial heating the water level is monitored with a low water cutoff(LWCO) sensor. When the water level in the boiler drops below the levelof the low water cutoff sensor, the burner is turned off until the waterlevel is brought back up to a safe level. These controls are well knownin the art.

One example is U.S. Pat. No. 6,390,027, issued to Lyons and Murray,entitled, “CYCLE CONTROL SYSTEM FOR BOILER AND ASSOCIATED BURNER,” whichis incorporated by reference. In the '027 design, a cycle control systemis used with a boiler to determine the presence of an adequate level offluid within the boiler.

In operation, an LWCO has a probe that extends into the boiler through asingle tapping. Generally, the probe has two electrically conductivesurfaces that are isolated from each other. An electrical signal isprovided to one of these conductive surfaces. When the water level isabove the level of the probe, the circuit between the conductivesurfaces is closed by virtue of the conductivity of the watersurrounding the probe. When the water level falls below the probe, thereis no conductivity between the metal conductive surfaces. Thus, thecircuit is open, and the control detects a low water condition.

Another component of monitoring boiler systems is information concerningthe temperature of the water in the boiler. There are many temperaturecontrol systems in the art currently used to monitor water temperaturein a boiler. Commercially available temperature controllers include, forexample, the Honeywell L7224U Aquastat Relay. In these devices, atemperature sensing thermistor is inserted into a hollow well. Thehollow well is then inserted within a tapping in the boiler and theboiler is filled with water. The thermistor is connected to a centralcontrol unit. The central control unit monitors the temperaturegradient, and is typically programmed to shut down the burner to preventthe water in the boiler from exceeding a preset limit. The centralcontrol unit may also be programmed to turn the burner ON to maintain aminimum boiler temperature.

In U.S. Pat. No. 5,340,019, issued to Bohan, Jr., et al., entitled,“ELECTRONIC AQUASTAT IN IMMERSIBLE CAPSULE,” a liquid immersibleelectronic Aquastat is taught in which a temperature responsive elementand substantially all associated electronic circuitry are arranged on acircuit board within a tubular capsule of liquid impervious material.The capsule or well houses a thermocouple, while conducting heat energyfrom the surface of the well to the temperature sensor.

A need exists to combine the two safety functions of monitoring for lowwater cutoff and temperature measurement in a single probe withsupporting control circuitry to allow it to perform in existing boilertappings, thus eliminating the need to drain the boiler to insert a newtapping.

In U.S. Pat. No. 5,111,691, issued to John, et al., entitled,“CONDUCTANCE/THERMAL LIMIT CONTROL APPARATUS AND METHOD,” a temperatureprobe is taught which mounts in a liquid container. The probe has aconductance electrode coupled to a conductance control circuit. Atemperature sensor is combined with this low water cutoff probe. Thiscontrol, however, does not allow for the ability to replace the sensorof an existing Aquastat such as the Honeywell devices described abovewithout draining the boiler and possibly the entire heating system.Furthermore, this design only provides high temperature limit with noprovision to turn the burner on to maintain a minimum boilertemperature, or to control the circulator pump on a call for heat.

One problem in the industry has been the reluctance to accommodatemultiple tappings for water cutoff probes and temperature sensor probes.This requires expensive redesigns of boiler castings to accommodate asecond hole in the boiler wall for the additional probe. It is desirableto combine the two measurement functions in a single probe, which can beinserted into a single well. It is further desirable to construct aprobe/well design that can accomplish the multiple measurements in asingle device that is interchangeable with existing well designscurrently available in the industry. In this manner, it is not necessaryto provide a new tapping or to drain existing boilers currently inoperation in order to incorporate the present invention. In addition, itis desirable for the present invention to maintain a minimum boilertemperature.

Another problem that occurs is when the control circuitry is set tomaintain a minimum water temperature and the temperature sensor is notin the boiler. In the prior art, the control circuitry would incorrectlydetermine that the water temperature is too low, and try to run theboiler, causing an unsafe, high temperature condition. This is generallyreferred to as a “run-away boiler” condition. In the present invention,if the dual probe sensor is connected to the control circuitry but notinserted into the well, the control circuitry will sense a low watercondition, and not allow the burner to fire.

SUMMARY OF THE INVENTION

Bearing in mind the problems and deficiencies of the prior art, it istherefore an object of the present invention to provide a probe forsensing water level (low water cutoff) and temperature in a single unit.

It is another object of the present invention to provide a removableprobe for sensing water level and temperature in a single unit thatallows for integration into an existing tapping.

It is another object of the present invention to provide a slideablyremovable probe in a well that may accommodate sensing functions of lowwater cutoff and/or temperature measurement within the integration of anexisting tapping.

It is yet another object of the present invention to provide a controlunit that allows a user to set the limits for temperature and monitorlow water conditions.

It is another object of the present invention to provide visual signalsto the user to indicate which functions, temperature and low water, arecurrently active.

A further object of the present invention is to provide a safe conditionwhen the probe sensor is connected to the control circuitry but notproperly inserted within the well, which would otherwise cause arun-away boiler condition.

Still other objects and advantages of the invention will in part beobvious and will in part be apparent from the specification.

The above and other objects, which will be apparent to those skilled inthe art, are achieved in the present invention, which is directed to aremovable probe insertable within a well in a boiler tapping comprisinga removable low water cutoff sensor in electrical communication with thewell interior by a resilient flexing connection, the low water cutoffsensor and the resilient flexing connection forming a slideablyremovable electrical connection.

The low water cutoff sensor includes a conductive member comprising asolidly-shaped conductive material, the solidly-shaped conductivematerial in electrical communication with the well interior, thesolidly-shaped conductive member and the resilient flexing connectionforming the slideably removable electrical connection without solderingor welding the conductive member to the interior of the well.

The low water cutoff sensor may further include a conductive nut forthreadedly securing into the boiler tapping, the conductive nut inelectrical communication with an interior wall of the boiler forming aconductive path between the interior wall of the boiler and the wellwhen water within the boiler interior surrounds and contacts the well,the conductive path is open when the water within the boiler interiordoes not surround or contact the well.

In a second aspect, the present invention is directed to a removableprobe insertable within a well in a boiler tapping comprising a lowwater cutoff sensor in electrical communication with the well interior,the electrical communication formed by a resilient flexing connection,the low water cutoff sensor including a conductive member comprising asolidly-shaped conductive material, the solidly-shaped conductivematerial in electrical communication with the well interior withoutsoldering or welding the conductive member to the interior of the well,such that the low water cutoff sensor and the resilient flexingconnection form a slideably removable electrical connection.

In a third aspect, the present invention is directed to system formonitoring low water cutoff and temperature in a boiler comprising: atemperature sensor within a housing inserted into a well within a boilertapping; a slideably removable low water cutoff sensor in electricalcommunication with the well interior; a resilient flexible connectorforming the electrical communication with the slideably removable lowwater cutoff sensor, such that the low water cutoff sensor senses avoltage potential of the well when in electrical communication with theresilient flexible connector; a conductive nut threaded for connectionto the well and in electrical communication with the boiler interiorwall; and a microcontroller including software for receiving andmonitoring the temperature sensor and the low water cutoff sensorinputs.

The temperature sensor may include at least one thermistor. Themicrocontroller may include a high impedance resistor to shift thetemperature sensor or the low water cutoff sensor inputs signals ofapproximately ±2.5 volts (p-p) or approximately 0-5 volts (p-p).

Software filtering is performed by the microcontroller at an approximaterate of 1/10 Hz, and approximately sixteen samples are measured andaveraged. The software may be designed to perform a second, long-termaverage with a sixteen-sample averaged value. The software may comparean averaged value to predetermined threshold conditions includingshorting, good or poor conductivity threshold, or an empty boilercondition.

The controller may perform boiler operations using calculations thatinclude outdoor temperature, indoor temperature, boiler returntemperature, or boiler supply temperature, or a combination of the same.

BRIEF DESCRIPTION OF THE DRAWINGS

The features of the invention believed to be novel and the elementscharacteristic of the invention are set forth with particularity in theappended claims. The figures are for illustration purposes only and arenot drawn to scale. The invention itself, however, both as toorganization and method of operation, may best be understood byreference to the detailed description which follows taken in conjunctionwith the accompanying drawings in which:

FIG. 1 depicts an assembly drawing of a sensor well.

FIG. 2 depicts an assembly drawing of the well of FIG. 1 with anelongated brass nut.

FIGS. 3A and 3B depict a combined low water cutoff and Aquastatthermistor insert for installation into the proposed embodiments ofFIGS. 1 and 2.

FIG. 4 is a wiring diagram for a control system.

FIG. 5 depicts the control system of the instant invention.

FIG. 6 depicts flow chart of one embodiment of the control system of thepresent invention.

FIG. 7 is an assembly drawing of a gas boiler control housing of thepresent invention having high/low temperature and low water cutoffindicators.

FIGS. 8A and 8B depict the temperature sensor assembly of the presentinvention.

FIG. 9 depicts the program flow for utilizing the dual probe design ofthe present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

In describing the preferred embodiment of the present invention,reference will be made herein to FIGS. 1-9 of the drawings in which likenumerals refer to like features of the invention.

The present invention teaches a dual functionality of temperaturecontrol measurement and low water cut-off measurement within a singletapping in a boiler. This dual functionality combines a low watercut-off and temperature sensor into one control utilizing a sensingelement suitable for use in an existing ¾″ tapping for typical boilers.The tappings generally comprise a threaded brass nut for insertion in aboiler housing wall, a hollow, cylindrical temperature/low water cutoffwell for protecting and securing the sensors, and an insulator(dielectric), which electrically separates the brass nut from thecylindrical well. The sensor well allows a user to insert thetemperature sensor and low water cutoff sensor without draining thesystem. Importantly, the sensor well may be used for both temperatureand low-water cutoff measurements. In this manner, the dual functioncapability may be employed in boilers where only a single tapping isavailable.

FIG. 1 depicts an assembly drawing of a well 10 of the presentinvention. A brass well nut 1 is securely and circumferentially attachedto the temperature/low water cutoff well or tube 3. Insulator 4 extendscircumferentially around a portion of well 3, electrically isolatingbrass nut 1 from well 3. In this manner, electrical connection betweenthe well 3 and brass nut 1 is communicated only by the conductivity ofsurrounding water. If the water level is below well 3, the electricalconnection is broken, and a low water cutoff condition is realized.Typically, well 3 is made of copper, although other conductive metalcombinations may be used with equal success. Importantly, well 3 extendsthrough, but makes no contact with, brass nut 1. Any contact wouldresult in the electrical shorting of the low water cutoff circuitry.Brass well nut 1 may be any other suitable, non-brass material, providedit can survive the exposure requirements in adverse boiler environments,and lend suitable conductivity for the proper operation of the low watercutoff control circuitry. The electrical isolation between well 3 andbrass nut 1 is controlled by insulator 4. Insulator 4 is preferably madeof a material that substantially resists electrical connection, such asa modified polyphenylene oxide resin (PPO), or the like. One suchexample is NORYL® N300X, which is a blend of polyphenylene ether (PPE)and polystyrene (PS).

Brass nut 1 includes a threaded portion, or some other appropriate meansfor connecting the probe assembly to the boiler. Importantly, brass nut1 allows well 10 to be inserted within the wall of a boiler above theminimum water line, and remain there indefinitely by creating awatertight seal upon installation. The connection of brass nut 1 to thewall of the boiler also allows well 10 to be in electrical communicationwith the boiler interior wall. Generally, in operation, portions of well3 and insulator 4 are exposed within the boiler interior to the water.Simultaneously, brass nut 1, which is in electrical communication withthe boiler interior wall, is also exposed to the water. When anelectrical signal is applied to well 3, it remains isolated from brassnut 1 as well as the boiler interior wall. In this manner, no electricalcommunication is established between well 3 and brass nut 1. This isbecause insulator 4 prohibits electrical conductivity. Under normaloperating conditions, the water level is high enough in the boiler tosurround and encompass exposed portions of well 3 and brass nut 1. Theconductivity of the water effectively bypasses the operation ofinsulator 4 and completes the low water cutoff circuit, connecting well3 to the boiler interior wall at brass nut 1. When electrical connectionis detected, the control circuitry connected to the probe determinesthat adequate water is in the boiler. When the water level is below well10, well 3 is no longer in electrical communication with the boilerinterior wall at brass nut 1. The absence of an electrical signal tocomplete the circuit, i.e., an open circuit, allows the system todetermine that the water level is sufficiently low, and subsequentlyshuts down the burner.

FIG. 2 depicts an assembly drawing of a well 10 a of the presentinvention with an elongated brass nut 11. Electrically, the well 10 aconfiguration of FIG. 2 is the same as the well 10 configuration of FIG.1.

FIGS. 3A and 3B depict a combined low water cutoff and thermistor insertfor installation into the proposed embodiments of FIGS. 1 and 2. Theprobe 20 contains preferably two thermistors per assembly (not shown),encased within a temperature sensitive thermoplastic (TPE) over-mold 23.As illustrated in FIGS. 3A and 3B, probe 20 is secured in well 3 by aresilient, compression-fit conductive member 24, such as a wire having aspring constant, a shaped wire clip (shown), a peripheral orsemi-peripheral resilient conductive band, or a solid-shaped conductivematerial capable of fitting within the well to ensure good electricalcontact with the well interior wall, and which may provide a compressiveforce that simultaneously holds or pushes an adjacent temperature sensoragainst the well interior wall. If conductive member 24 is in the formof a resilient wire, it is preferably constructed of beryllium copper(BeCu). Conductive member 24 is configured to extend upward from thesurface of probe 20. Conductive member 24 terminates on a conductorwithin the assembly. In doing so, conductive member 24 makes electricalconnection with well 3, which is exposed to the boiler waterenvironment. This connection allows a low water cutoff signal topropagate from the controller circuitry, making a circuit with well 3and the electrically isolated brass nut 1 when conductive water ispresent. Conductive member 24 forms part of the contact path for the lowwater cutoff circuit. The water provides the connection from well 3 tobrass nut 1, thereby bypassing insulator 4. When water is no longerpresent, the low water cutoff circuit is open, i.e., insulator 4 doesnot allow the signal to propagate, and a low water level is detected.The conductive member 24 secures the thermistor assembly within a wellby forming a compression fit, while simultaneously providing a securefitting for electrical contact for the low water cutoff signal. Thisdesign readily accommodates existing wells that were not otherwiseconstructed for this purpose. The probe of the present invention may beplaced in a temperature sensor well design that is unable to accommodatea low water cutoff application. The supporting control circuitry willmeasure temperature, while the low water cutoff electrical signalmonitors resistance. If the probe is in a temperature-sensor only well,the conductive member will sense zero ohms of resistance and temperaturesensing will remain active while the low water cutoff function isinactive. This allows the present invention to replace an existing,non-dual function probe, and provide at least the same functionality asthe probe it replaced.

The conductive member ensures that the probe of the present invention isinserted in the well. In contrast, if a probe is not inserted in thewell, the temperature measurement cannot be sensing boiler temperature.This would cause a controller connected to a prior art probe to initiatea continuous firing of the boiler, otherwise known as a run-away boilercondition. However, in the present invention, a signal from theconductive member will ensure that the probe is inserted. Ensuring thatthe probe is installed in the well addresses this run-away boilercondition in a manner that is unique to the present invention.

In the preferred embodiment, the encapsulated thermistor 20 has a 30K-ohm resistance at 25° C. with an operating temperature range on theorder of −40° C. to +125° C. Clearly, these specifications are boilerdependent, and may be adjusted for specific applications. In operation,probe 20 is placed in well 3. When inserted, conductor 24 is forced downinto channel 26. This ensures that conductive member 24 will remain inpressure contact with the interior wall of well 3. The wires 28connected to, and extending from, probe 20, are covered by a heat-shrinkwrap 30. This heat-shrink wrap serves the dual function of insulatingthe wiring system from the environment, and also providing rigidity tothe wire structure. For the preferred two-thermistor design, fourconductors are used, such as 26 AWG 7/34 T.C., or the like, withinsulation and an overall TPE cable jacket. The rigidity provided by thewrapping allows the thermistor assembly, including the compression-fitconductive member 24, to be push-inserted within an existing wellwithout collapsing onto itself. In contrast, the thermistor disclosed inU.S. Pat. No. 5,111,691 issued to John, teaches wires without any meansfor rigidity, mainly because the John disclosure does not suggest orteach using the thermistor assembly for replacement in wells that werenot specifically designed for it. The '691 patent also does not includea wire member assembly necessary to engage with the well simultaneouslyfor a low water cutoff signal and temperature sensing signal.

Thus, the present invention allows for a dual probe combiningtemperature measurement and low water cutoff to be inserted within anexisting well of a boiler without requiring a new tapping. The probe canbe inserted within an existing well because of the rigidity of the wiresystem that allows the thermistor to be friction fit while providing forelectrical connection for the low water cutoff signal. The controlcircuitry may then monitor safe operation of the boiler. However, dualsensing may be accommodated only if the existing well includes adielectric spacer for the low water cutoff signal conductivitymeasurement.

FIG. 4 is a wiring diagram 40 for a control system. The wiring diagramdepicts how a thermostat 42, circulating pump 44, burner 46, andmulti-zone controller 48 are connected in a preferred embodiment.

FIG. 5 depicts the control system 50 of the instant invention. Controlsystem 50 has controls that allow for adjusting the low temperaturesetting 52, high temperature setting 54, and the temperaturedifferential 56. A display 58 is used for indicating the watertemperature to the user or technician. Diagnostic lights 51, 53, 55, and57 indicate active temperature, high temperature, active low watercutoff, and low water, respectively.

In operation, a temperature control circuit is used in conjunction withthe temperature sensor. The temperature sensor inputs a temperaturesignal for sensing a high temperature range with adjustabledifferential. The measured temperature is used to determine theoperation of the burner through comparator circuitry and relays for thesafety functioning of the burner, e.g., a high temperature condition mayrequire burner shut-off and a low temperature condition may require theburner to be turned on. A thermostat signal is also used as an input toallow for a “demand heat” condition.

A conductance sensor is used for measuring the variable conductivity ofthe water in the boiler. The sensor receives an AC source signal andprovides a variable resistance to the signal based on the conductivityof the water. The variable resistance forms a resistor divider networkwith a predetermined series resistance. The AC source signal (railvoltage) is preferably a 5 volt signal operating at approximately400-500 Hz. The probe input is on the order of 100 mV of the rail.Specifically, the source signal is preferably sinusoidal with anamplitude span of approximately +2.5 volts to −2.5 volts (peak-to-peak).Generally, there are no active electronics within the sensor, althoughthe present design does not preclude the addition of such devices. Theresistance divider formed by a series resistor and a variableresistance, which represents the measured water conductance, acts toattenuate the source signal in an amount proportional to the waterconductivity.

Referring to FIG. 6, the probe input 61 is then directed to a unitybuffer 62, which provides a high impedance for interfacing with theanalog input of the microprocessor 63. The signal is biased at +2.5volts through a high impedance resistor. This shifts the signal from±2.5 volts (p-p) to 0-5 volts (p-p), which enables it to be receivedproperly at the analog input of microprocessor 63. No amplification isperformed during this biasing. The probe input port is voltage surgeprotected by a diode.

Microprocessor 63 receives the buffered probe signal at an analog input64 to microprocessor 63. The analog input signal is normally sampled insequence with a drive signal (AC source signal). Microprocessor 63performs a sample-and-hold function for a high output drive signal and alow output drive signal, respectively. The signal's peak-to-peak voltageis then measured. Internal to the microprocessor is an analog-to-digital(A/D) converter that converts the bias signal returned from the probeinto a digital value with 8-bit resolution (0-255).

Software filtering is performed by the microprocessor at a preferredrate of approximately 1/10 Hz. Sixteen samples are measured and averagedin order to eliminate or account for externally induced noise. A secondaverage (long-term average) is performed with the sixteen-sampleaveraged value. The resultant averaging function filters out adverseeffects due to air bubbles and probe-induced or probe-coupledtransients. The measured, averaged value is then compared via softwareto threshold conditions such as: a) shorting; b) good/poor conductivitythreshold; and c) an empty boiler condition. As the measurement softwareloop progresses, the resultant determination (short, good conductor,etc.) must be shown to persist for a predetermined number of cyclesbefore a declaration may be made and action taken. If the measurementcondition is removed before the predetermined number of cycles isaccumulated, a counter is reset and the measurement cycle is repeated.Once an actionable condition is determined, the user is notified by aseries of LED indicators 65 and appropriate action is taken, e.g., theboiler may be shut down for a “no water” condition.

The action taken by the controller includes toggling a burner relay 66.Relay 66 is turned on or driven by a relay driver circuit 67 whichrequires redundant burner signals to ensure that any action affectingburner operation is not based on faulty circuitry.

Preferably, four settings are available for the temperature display 68of the present invention: high temperature 69; low temperature 70; hightemperature plus differential 71; and low temperature plus differential72. The high temperature settings 69 and 71 limit the boiler watertemperature to a safe operating temperature. The low temperaturesettings 70 and 72 maintain a minimum temperature in the boiler. In acold start condition, the burner does not fire unless there is a callfor heat from the system thermostat 73. In the low temperature sensorlimit of the present invention, turning the temperature control settingto off, turns the controller into a cold start apparatus.

FIG. 7 is an assembly drawing of a gas control housing 74 of the presentinvention having high/low temperature and low water cutoff indicators75. Probe well 76 is shown drawn to approximate scale. Housing 74comprises a lower module 77, a printed circuit board assembly 78, and ahousing cover 79. Circuit board assembly 78 includes electronics, thehigh temperature and low water indicators, a temperature probe check (HTactive), a water probe check (LW active), high temperature settings,high temperature differential, and burner firing signals.

FIGS. 8A and 8B depict the temperature sensor assembly 80 of the presentinvention. The conductors 82 from each of two thermistors 84 are wrappedin semi-rigid heat shrink tubing 86 and terminated with connectors 88,preferably using terminals such as AMP P/N 770666, or the like, and acorresponding connector, such as AMP P/N 770602-4, or the like. The heatshrink tubing is preferably a polyolefin heat shrink sleeve orequivalent. The thermistors are housed in a plastic or metal housing 81.In one embodiment the thermistors are first encapsulated in a resin,such as blue hysol or the like. Conductors 82 are soldered to eachthermistor lead. The solder joints are protected by an adhesive linedpolyolefin sleeve, preferably a sleeve with a temperature rating on theorder of 135° C. Sharing the same housing is beryllium copper conductorclip 83, which connects to its own dedicated conductor 85. Clip 83extends outside of housing 81 in order to make contact with the metalinterior wall of the well. Clip 83 may be formed from 22 AWG wire orother resilient material. Clip 83 helps position the thermistors 84,which are opposite the clip, against the well.

Many different versions of temperature probes are suitable for use inthe present invention. In one embodiment, a preferred probe includesepoxy coated point matched disc thermistors with nickel PTFE insulatedlead wires. One such probe may be comprised of NTC thermistors from GE.These probes have a solid-state sensor, strong mechanical strength, anda wide operating temperature range of about −50° C. to 150° C. Anothersuch sensor is a Betatherm Corporation sensor, which is also a ceramicchip NTC thermistor design with nickel plated CP wire, and glassencapsulating material. These probes are representative of the types ofprobes which may be used in the present invention; however, the presentinvention may accommodate other probe designs, and is not limited to theprobes identified above, provided each probe meets the physicalrestraints of the well design, and the environmental restrictions onboiler operation.

FIG. 9 depicts the program flow 90 for utilizing the dual probe designof the present invention. Upon initiating the power up sequence 91, theburner 92 and circulator 94 are off. The water sensor is first initiated96. For a low water condition, the low water LED is activated 98 andburner 92 and circulator 94 are turned off or kept off. For a high watercondition, the low water LED is either switched off or kept off 100. Atemperature measurement is made 102. If the temperature is low, thecirculator is turned off or kept off 104. The high temperature LED isturned off or kept off 106, as the case may be, and the burner isactivated or turned on 108. If the temperature measurement 102 is notlow, the thermostat input is monitored for a call for heat 110. If thereis no call for heat, the maximum temperature limit is checked 112. Ifthe maximum temperature is reached, the high temperature LED is turnedon 114 and the burner 92 and circulator 94 are turned off. If themaximum temperature limit 112 is not attained, the high temperature LED116 remains off, and again the burner 92 and circulator 94 also remainoff. If the thermostat input 110 calls for heat, the circulator isturned on 118. The maximum temperature limit is monitored 120. When themaximum temperature is reached, the high temperature LED is turned on122, and the burner is turned off 124. The water sensor is thenmonitored 96. If Maximum temperature is not reached, the hightemperature LED 106 is turned off or kept off and the burner 108 isturned on or kept on. The water sensor 96 is then monitored.

Importantly, the present invention's controller allows for externaltemperature inputs as well as various boiler system temperature inputs.This would include outdoor temperature, boiler return temperature,boiler supply temperature, indoor temperature, and the like. This allowsfor efficient burner operation under various environmental and systemconditions. For example, in this manner, an outside temperature or callfor heat is monitored, and the boiler is limited to the outdoor resetcontroller conditions. Thus, the dual function sensors are integratedwith a controller that monitors external environmental temperature. Ifthe controller system monitors a high outside temperature, it wouldregulate its temperature accordingly. Otherwise, the system would notdistinguish between a moderate 50° day and a cold 10° day, insomuch asit will work all the time as if it is in an environment of a cold dayall year long. It will consistently heat the water to a maximumtemperature without regard for the outside temperature. By incorporatingboiler system and environmental temperature measurements, the system canprovide significant energy efficiency.

One feature of the present invention is the ability to replace sensorsfrom existing controllers without replacing the wells, that is, it hasthe unique ability to be interchangeable with current systems. In somesystems, it is possible that the interchange of the present sensorsystem into an existing system will not allow the dual function of thepresent invention to be completely activated. In these circumstances,only temperature function may be employed. Indicator lights will signalwhich functions are active.

While the present invention has been particularly described, inconjunction with a specific preferred embodiment, it is evident thatmany alternatives, modifications and variations will be apparent tothose skilled in the art in light of the foregoing description. It istherefore contemplated that the appended claims will embrace any suchalternatives, modifications and variations as falling within the truescope and spirit of the present invention.

Thus, having described the invention, what is claimed is:
 1. A removableprobe insertable within a sensor well in a boiler tapping, the probecomprising a removable low water cutoff sensor in electricalcommunication with an interior of said sensor well, said probe formingelectrical contact with said interior of said sensor well by a resilientflexing connector, said low water cutoff sensor and said resilientflexing connector forming a slideably removable electrical connection.2. The removable probe of claim 1, wherein said low water cutoff sensorincludes a conductive member comprising a solidly-shaped conductivematerial, said solidly-shaped conductive material in electricalcommunication with said well interior, said solidly-shaped conductivemember and said resilient flexing connector forming said slideablyremovable electrical connection without soldering or welding saidconductive member to the interior of said well.
 3. The removable probeof claim 1, wherein the low water cutoff sensor further includes aconductive nut for threadedly securing into said boiler tapping, saidconductive nut in electrical communication with an interior wall of saidboiler and forming a conductive path between said interior wall of saidboiler and said sensor well when water within said boiler interiorsurrounds and contacts said sensor well, and wherein said conductivepath is open when said water within said boiler interior does notsurround or contact said sensor well.
 4. A removable probe insertablewithin a sensor well in a boiler tapping, the probe comprising a lowwater cutoff sensor in electrical communication with an interior of saidsensor well, said probe forming electrical contact with said interior ofsaid sensor well by a resilient flexing connector, said probe includinga conductive member comprising a solidly-shaped conductive material,said solidly-shaped conductive material in electrical communication withsaid interior said sensor well through said resilient flexing connectorwithout soldering or welding said conductive member to the interior ofsaid sensor well, such that said low water cutoff sensor and saidresilient flexing connector form a slideably removable electricalconnection.
 5. A system for monitoring low water cutoff and temperaturein a boiler comprising: a temperature sensor within a housing insertedinto a sensor well within a boiler tapping; a slideably removable lowwater cutoff sensor in electrical communication with an interior of saidsensor well; a resilient flexible connector forming electrical contactat the junction of said interior of said sensor well and said slideablyremovable low water cutoff sensor, such that said low water cutoffsensor senses a voltage potential of said sensor well when in electricalcommunication with said resilient flexible connector; a conductive nutthreaded for connection to said well and in electrical communicationwith said boiler interior wall; a microcontroller including software forreceiving and monitoring said temperature sensor and said low watercutoff sensor inputs.
 6. The system of claim 5 wherein said temperaturesensor includes at least one thermistor.
 7. The system of claim 5wherein said microcontroller includes a high impedance resistor to shiftsaid temperature sensor or said low water cutoff sensor inputs signalsof approximately ±2.5 volts (p-p) or approximately 0-5 volts (p-p). 8.The system of claim 5 wherein software filtering is performed by saidmicrocontroller at an approximate rate of 1/10 Hz, and approximatelysixteen samples are measured and averaged.
 9. The system of claim 5including having said software perform a second, long-term average witha sixteen-sample averaged value.
 10. The system of claim 5 includinghaving said software compare an averaged value to predeterminedthreshold conditions including shorting, good or poor conductivitythreshold, or an empty boiler condition.
 11. The system of claim 5including having said controller perform boiler operations usingcalculations that include outdoor temperature, indoor temperature,boiler return temperature, or boiler supply temperature, or acombination of the same.